Background An altered peripheral perfusion with skin vasoconstriction has been observed in the early phase of sepsis. The peripheral perfusion index (PI) derived from the pulse oximetry signal is an easy and non-invasive method to assess peripheral perfusion.

Objective To evaluate the PI as an early predictor of infection in asymptomatic newborns with antenatal risk factors for infection.

Methods 400 term or near-term newborns were randomly, non-consecutively assessed for PI by pulse oxymeter in the first 8 h. 118 had risk factors for infection and were tested in the second day of life for C-reactive protein (CRP) and full blood count and were eventually treated for infection. An attending neonatologist was unaware of the PI value.

Results PI was significantly lower in infants with a subsequent raise in CRP compared with CRP-negative infants (p<0.0001). PI could also differentiate a borderline from a positive CRP (0.5–1 mg/dl and >1 mg/dl, respectively). In the receiver operator characteristic curve analysis, a cut-off value of 1.38 had a 98% sensitivity and a 87% specificity for predicting a CRP >0.5 mg/dl; a PI cut-off value of 1.07 had 98% sensitivity and 89% specificity for predicting a CRP >1 mg/dl.

Conclusion A single value of PI measured in the first 8 h of life has high specificity and sensibility for predicting a positive CRP in the second day of life and therefore may be an easy, rapid and non-invasive tool in the diagnosis of infection in apparently healthy newborns with antenatal risk factors.